Microprocessors are used today f or performing the internal operations of modern instruments. Additionally, computers and microprocessors are used to control test and measurement systems. The primary method used for interconnecting and communicating between instruments and control computers (controllers) is the IEEE 488 bus.
The IEEE 488 bus is essentially an electrical signal transmission bus with a predefined set of lines. A set of predefined protocols govern the methodology for transferring information over the bus from a controller to specified devices, and vice versa. By using an industry standard bus, the manufacturers of a wide variety of instruments can ensure that standard software packages and interface circuits can be used to connect their instruments to microprocessor based controllers. That is,, purchasers of these instruments do not need to buy a different customized controller for each instrument, because all such instruments use the same set of signal lines and the same set of communication protocols.
Integrated circuits (chips) are used to interface the computer or microprocessor to the IEEE 488 bus. The IEEE 488 interface integrated circuits (IEEE 488 chips) that exist today were designed and developed prior to the publication of the latest instrumentation standards: ANSI/IEEE 488.1-1987 and ANSI/IEEE 488.2-1987, both of which are hereby incorporated by reference. These chips, for the most part, conform to an earlier standard: IEEE Std 488 -1978, also hereby incorporated by reference.